Imidazolinium cationic surfactants may be prepared by reaction of the corresponding imidazoline compound with dimethyl sulfate. See Bajpai, D., Fatty Imidazolines: Chemistry, Synthesis, Properties and Their Industrial Applications, J. Oleo Sci., Vol. 55, No. 7, 319-329 (2006), pp. 321-322. A hydroxy substituted fatty acid imidazoline is disclosed as CAS registry compound no. 93858-34-5, having a molecular formula C40 H75 N3 O3. Imidazolines are used in pharmaceutical compositions and as corrosion inhibitors.
Debonder compositions are used in connection with the manufacture of absorbent paper products such as paper tissue and paper towel to adjust tensile strength and provide softness. Among the most effective compounds are quaternary ammonium surfactants which are sometimes used together with nonionic surfactants. Debonders are used with numerous additives such as wet strength agents and so forth. See U.S. Pat. No. 3,755,220 to Freimark et al. (1973), Col. 2, lines 1-10. U.S. Pat. No. 6,969,443 to Kokko discloses debonder compositions, including imidazolium salts in combination with nonionic surfactants. This reference also discloses the use of additives, including charge modifiers, wet strength resins, retention aids and auxiliaries such as carboxymethylcellulose. See Cols. 10-12. So also, U.S. Pat. No. 6,649,024 to Oriarian et al. discloses absorbent products incorporating a variety of cationic debonders, including di- or trialkyl ammonium salts. United States Patent Application Publication No. US2004/0163182 to Nguyen discloses nonionic surfactants used in combination with amide substituted imidazolinium salts. See paragraph [0013]. U.S. Pat. No. 4,959,125 to Spendel (1990) discloses manufacture of absorbent sheet with ampholytic or zwitterionic surfactants. See Col. 11, lines 21-46. Note, also, U.S. Pat. No. 6,245,197 to Oriaran et al. which discloses mixtures of cationic quaternary ammonium surfactants and anionic surfactants.
Ricinoleic acid is disclosed for the manufacture of surfactants in numerous references. See U.S. Pat. No. 4,254,255 to Löbach et al., Col. 2, lines 33-57. Ricinoleic acid is disclosed for the manufacture of quaternary surfactants as is seen in U.S. Pat. No. 5,420,315 to Uhrig et al., throughout. See claim 1. U.S. Pat. No. 6,623,746 to Wadle et al. discloses polyol esters of ricinoleic acid at Col. 5, lines 52 and the '746 patent likewise discloses a variety of zwitterionic surfactants including imidazolines at Col. 6, lines 31 and following. U.S. Pat. No. 7,585,494 to Lange et al. discloses ester-containing cationic surfactants including surfactants containing ricinoleic acid. See Cols. 39-40, note especially Col 40, lines 1-5 which mentions imidazoliniums.
A significant drawback of conventional systems using quaternary ammonium salts is that these compounds contribute significantly to titratable charge and change zeta potential. Controlling charge and zeta potential of the furnish in the headbox is critical to papermachine performance especially retention of papermaking solids in the final product. The problem with adding too much cationic additive is that it will exceed the adsorption capacity of the fiber surfaces, based on either the surface area or the limited extent of negative charge of the surfaces of fibers and other solid surfaces in the furnish. Excess cationic additives beyond what adheres to the fibers is likely to cause foam, high biological oxygen demand (BOD) levels in the effluent, and poor retention and drainage. Conventional charge control agents such as carboxymethyl cellulose can adversely impact softness of the product. The use of charge control agents may be reduced or even avoided entirely when using the process and compositions of the present invention.